I love the look and the sleek, discreet design of the pen; you can tell it's high quality. When the pen works properly, it's very pleasant to vape, but out of 25 pens I've used, 6 or 7 never worked at all, producing no vapor even when the pen was heating up. So I wasted the pens, which contained 2ml each. And another thing, I don't know if it would be feasible. But why is the filling hole so small? Would making it bigger harm the vaping quality? That's a question. I wonder and that I ask you and thank you